Constructing tunable bimodal porous structure in ultrahigh molecular weight polyethylene membranes with enhanced water permeance and retained rejection performance

The low porosity and pore connectivity of ultrahigh molecular weight polyethylene (UHMWPE) membranes reduced membrane performance and limited its application in water treatment. In this work, the bimodal porous structure including two different grades and independent pore size distributions was constructed in UHMWPE membrane via thermally induced phase separation and sodium chloride (NaCl) leaching (TIPS-NL). Large pores (5–10 μm) were connected by small pores (0.09–0.15 μm), in which both pore sizes can be adjusted independently. When the large pores content is 35 vol% of the small pores, the water permeance of the separation membrane reaches 1177 L/(m2 h bar), which is about 16 times higher than that of the single-distributed small pores 74 L/(m2 h bar), and the particle, whose size is larger than 0.16 μm, can be well intercepted. Because the content of small pores in the bimodal porous structure is enough to separate the large pores, the rejection property of the UHMWPE membrane is also preserved. According to the particle size to be separated, the rejection ratio and permeance can be improved by simply adjusting the size and content of small and large pores. This work provided a new perspective for the fabrication of high-performance UHMWPE membranes by TIPS-NL.